AWStats is a free powerful and featureful tool that generates advanced web, streaming, ftp or mail server statistics, graphically.
This log analyzer works as a CGI or from command line and shows you all possible information your log contains, in few graphical web pages. It uses a partial information file to be able to process large log files, often and quickly. It can analyze log files from all major server tools like Apache log files (NCSA combined/XLF/ELF log format or common/CLF log format), WebStar, IIS (W3C log format) and a lot of other web, proxy, wap, streaming servers, mail servers and some ftp servers.
AWStats works from the command line but also as a CGI, it can work with major web hosting provider which allow Perl, CGI and log access.
Many self-hosted Moodle installations (e.g. San Francisco State University) are using AWStats to come up with statistics of what Web browsers are most popular among visitors (of the moodle site), where visitors were coming from, and the most popular pages, etc.